August 2019 NY Regents Chemistry Exam
46 Given the equation representing a reaction: 2Ca(s) + O2(g) → 2CaO(s) During this reaction, each element changes in (1) atomic number (2) oxidation number (3) number of protons per atom
(4) number of neutrons per atom
Solution: This is a redox reaction since Ca has an oxidation number of 0 as a reactant and +2 as a product. Similarly, oxygen goes from 0 to -2. Each elements changes in oxidation number.
Answer: 2
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